Goldblum, D. and M.C. Kwit. 2012. The relative photosynthetic contribution of old and new fronds of the wintergreen fern Dryopteris carthusiana, Ontario, Canada. Bulletin of the Torrey Botanical Society. 139: 270-282.

Goldblum, D. (2010). The geography of white oak’s (Quercus alba L.) response to climatic variables in North America and speculation on its sensitivity to climate change across its range. Dendrochronologia. 28: 73-83. Abstract

Goldblum, D. and S.W. Beatty. (1999) Influence of an old field/forest edge on a northeastern United States deciduous forest understory community. Journal of the Torrey Botanical Society. 126: 335-443. Abstract

Abstract If current temperature trends continue and increase as predicted by general circulation models, the persistence and migration of sugar maple (Acer saccharum) at its northern limit will become crucial to its continued existence in North America. Specifically, anthropogenic warming may affect germination success and growth of sugar maple. To evaluate this potential limitation, our study addresses two questions. The first involves a growth chamber: Do temperatures at and above (1°, 7°, and 14° C) sugar maple's optimal germination temperature affect its germination? The second involves a common garden: Do sugar maple germination and subsequent growth and mortality rates show evidence of geographic variation under current climatic conditions? While sugar maple germinated successfully at 7° C in the lab, field results suggest that other environmental variables may limit its future establishment as climate changes. Germination of seeds from sugar maple's northern range limit was significantly reduced under warmer conditions, and subsequent seedling mortality rates were significantly increased when grown at a more southerly latitude. Local adaptation was evident with respect to germination, survival, and growth in the field. Ultimately, results from this study further the understanding of how predicted anthropogenic climate change may affect the regeneration of sugar maple in the future.

AbstractThe ability to model forest distributions in light of anthropogenic disturbance requires a thorough understanding of how trees respond to their physical and climatic environment. The primary objective of this study is to determine how four environmental variables (elevation, latitude, slope angle, and slope aspect) affect the distribution of seven common tree species (Acer saccharum, Betula alleghaniensis, Betula papyifera, Abies balsamea, Picea glauca, Thuja occidentalis, and Acer spicatum) using both regression tree analysis (RTA) and canonical correspondence analysis (CCA) techniques. In general, within the study area, Acer saccharum, Abies balsamea, and Thuja occidentalis abundance was controlled by elevation and latitude, whereas the other species showed limited response to the measured environmental variables. While CCA and RTA showed similar patterns, RTA allows for a more nuanced evaluation of species-environment interactions. Given that the study area encompasses Acer saccharum's northern limit, there were differences in the response of Abies balsamea to environmental conditions in the absence of Acer saccharum. Top

AbstractThe goal of this research was to assess the health and physiological stress of understory balsam fir (Abies balsamea) seedlings and saplings within Lake Superior Provincial Park (LSPP) in Ontario, Canada to provide an indication of the degree to which they are affected by ambient light levels. The photochemical efficiency of balsam fir photosystem II was tested by measuring fluorescence. Seedlings and saplings within four sites were sampled and measured for their daily photochemical efficiencies. It was hypothesized that the sampled balsam fir would display little, if any, light stress because balsam fir is relatively shade tolerant and the study area is located near the central portion of balsam fir’s range, theoretically providing optimum growing conditions. Overall, balsam fir exhibited relatively little variation in photosystem stress, particularly across size classes and location; however photosystem stress varied by time of day (greater stress at midday and afternoon) and presence of sunspots. Top

AbstractEcotones have been subject to significant attention over the past 25 years as a consensus emerged that they might be uniquely sensitive to the effects of climate change. Most ecotone field studies and modeling efforts have focused on transitions between forest and non-forest biomes (e.g. boreal forest to Arctic tundra, forest to prairie, subalpine forests to alpine tundra) while little effort has been made to evaluate or simply understand forest–forest ecotones, specifically the deciduous forest – boreal forest ecotone. Geographical shifts and changes at this ecotone because of anthropogenic factors are tied to the broader survival of both the boreal and deciduous forest communities as well as global factors such as biodiversity loss and dynamics of the carbon cycle. This review summarizes what is known about the location, controlling mechanisms, disturbance regimes, anthropogenic impacts, and sensitivity to climate change of the deciduous forest – boreal forest ecotone.Top

Goldblum, D. (2010). The geography of white oak’s (Quercus alba L.) response to climatic variables in North America and speculation on its sensitivity to climate change across its range. Dendrochronologia. 28: 73-83.Abstract: Dendrochronological analysis is used to determine white oak’s (Quercus alba L.) sensitivity to mean monthly temperature and monthly precipitation for the entirety of its range in the United States. Throughout much of its range, white oak is sensitive to summer precipitation (positive), summer temperature (negative), and previous season latesummer and fall precipitation (positive). Spatially, populations of white oak in the western and central portion of its range are most highly correlated with these variables, while Appalachian and eastern populations show little sensitivity to monthly climate variables. White oak’s radial growth rate in light of anthropogenic climate change (based on regional and downscaled climate models) may be most reduced in the far western portion of its range (Illinois and Missouri), whereas eastern populations are less likely to be adversely affected.Top

Kwit, M.C., L.S. Rigg, and D. Goldblum. (2010). Sugar maple seedling carbon assimilation at the northern limits of its range: the importance of seasonal light. Canadian Journal of Forest Research. 40: 385-393.Abstract: Dendrochronological analysis is used to determine white oak’s (Quercus alba L.) sensitivity to mean monthly temperature and monthly precipitation for the entirety of its range in the United States. Throughout much of its range, white oak is sensitive to summer precipitation (positive), summer temperature (negative), and previous season latesummer and fall precipitation (positive). Spatially, populations of white oak in the western and central portion of its range are most highly correlated with these variables, while Appalachian and eastern populations show little sensitivity to monthly climate variables. White oak’s radial growth rate in light of anthropogenic climate change (based on regional and downscaled climate models) may be most reduced in the far western portion of its range (Illinois and Missouri), whereas eastern populations are less likely to be adversely affected.Top

Goldblum, D. (2009). Sensitivity of corn and soybean yield in Illinois to air temperature and precipitation: the potential impact of future climate change. Physical Geography. 30: 27-42.Abstract: Dendrochronological analysis is used to determine white oak’s (Quercus alba L.) sensitivity to mean monthly temperature and monthly precipitation for the entirety of its range in the United States. Throughout much of its range, white oak is sensitive to summer precipitation (positive), summer temperature (negative), and previous season latesummer and fall precipitation (positive). Spatially, populations of white oak in the western and central portion of its range are most highly correlated with these variables, while Appalachian and eastern populations show little sensitivity to monthly climate variables. White oak’s radial growth rate in light of anthropogenic climate change (based on regional and downscaled climate models) may be most reduced in the far western portion of its range (Illinois andMissouri), whereas eastern populations are less likely to be adversely affected.Top

Abstract: Throughfall and precipitation pH were observed for one growing season in an undisturbed mixed deciduous-conifer forest on the east shore of Lake Superior in Ontario. Rainfall and throughfall were collected for pH analysis from late-May through mid-August under the dominant tree species. From a total of 18 measureable rainfall events, pH of deciduous (sugar maple and paper birch) and coniferous (white spruce and balsam fir) throughfall was significantly less acidic than the incident rainfall for nine of the events; particularly for events following deciduous canopy leafout. Deciduous and coniferous throughfall pH differed significantly from each other for four of the 18 rain events throughout the middle of the growing season. Paper birch had the least acidic throughfall and sugar maple, white spruce, and balsam fir throughfall were generally similar and more acidic. The spatial heterogeneity of throughfall chemistry as controlled by overstory species composition, in addition to numerous other environmental factors that differ at fine spatial scales in forest understories, may play an important role in mediating germination, growth rates, carbon assimilation rates, and mortality of understory tree seedlings.Top

Abstract: We consider the implications of climate change on the future of the three dominant forest species, sugar maple (Acer saccharum Marsh.), white spruce (Picea glauca (Moench) Voss), and balsam fir (Abies balsamea (L.) Mill.), at the deciduous-boreal forest ecotone, Ontario, Canada. Our analysis is based on individual species responses to past monthly temperature and precipitation conditions in light of modeled (general circulation model) monthly temperature and precipitation conditions in the study area for the 2080s. We then consider the tree species sensitivity to past climate with predicted conditions for the 2080 period. Sugar maple, located at its northern limit in the study area, shows the greatest potential for increased growth rates under the predicted warming and altered precipitation regime. White spruce is likely to benefit less, while the understory dominant balsam fir is likely to experience a decrease in growth potential. These projected changes would enhance the future status of sugar maple at its northern limit and facilitate range expansion northward in response to global warmingTop

Abstract: The transition from deciduous forest to boreal forest is abrupt regionally and topographically in Lake Superior Provincial Park, Ontario, Canada. The northern range limit of Acer saccharum is coincident with the forest transition to boreal forest. The goal of our study was to characterize the distribution of A. saccharum seedlings at the transition zone to determine if variability in seedling demographics and genetics with topographic position and along a short north-south gradient was evident. Seedling density, size, age, and growth were evaluated in permanent plots across the regional transition zone, and at the south-facing, ridge top and north-facing limits across the topographic transition. Growth over five years was determined by measuring the distance between terminal bud scars, and compared with regional climate data. Genetic material was collected and analyzed from two of these sites. No significant differences were detected in density or growth of Acer saccharum across the regional transition, but mean age increased and height decreased as the limit was approached. Across the topographic transition, ridge top seedling densities were greater than south-facing or north-facing limits. Genetic variability was substantial with no cohort preference for topographic position detected.Top

Abstract: Sugar maple reaches its northern limit along the eastern shore of Lake Superior marking the transition from the deciduous forest of eastern North America to a predominantly boreal forest community. In light of regional warming trends over the past 100 years and projections for even warmer conditions in the future we sought to characterize the current age structure and regeneration status of both sugar maple and boreal tree species within this ecotone zone. Within Lake Superior Provincial Park (Ontario, Canada) a series of west-east trending hills create numerous deciduous-boreal transition zones as sugar maple occupy uplands and boreal species occupy valley bottoms, then once north of the sugar maple limit, boreal species dominate all topographic positions. Unlogged forest stands were sampled in the transition zone on ridges and slopes both north and south of the sugar maple limit. Overall tree density and basal area in sugar maple and boreal stands was similar across the ecotone, but seedling density was significantly higher in plots dominated by sugar maple. Moreover, sugar maple seedlings, but not saplings, were found slightly beyond the adult sugar maple tree limit indicating the potential for range expansion may be limited by microclimatic variables, namely cold air drainage.Top

Abstract: Population size-structures, seed production, canopy seed storage (serotiny), and recruitment were investigated in relation to fire, drought and disease for a pair of co-occurring resprouting and non-sprouting shrub species from the genus Hakea (Proteaceae) in fire-prone Eucalyptus woodlands in western Victoria, Australia. The non-sprouter species, Hakea decurrens, showed faster height growth, higher seed production and higher seed viability than the resprouter, Hakea rostrata. Population size structures in stands up to 24 years since last fire showed no evidence of inter-fire recruitment for either species. Following a fire in 1990 in a mixed species stand 15-20 years old, the estimated number of viable seeds released from canopy-stored seed banks was approximately equal for both species. However, the rate of seedling establishment in the first year was about 10 times higher, and seedling suvivorship over the first 5 years was seven times higher, for the non-sprouter. Seedlings of Hakea decurrens and resprouts of Hakea rostrata began to produce seeds within three years of the last fire, while the few surviving seedlings of Hakea rostrata showed no evidence of reproductive maturity after six years. Inter-fire recruitment was recorded for the non-sprouter, Hakea decurrens, in the oldest stand (burned in 1967) between 24 and 28 years since last fire. This was associated with an increased rate of seed release from serotinous fruits due to the onset of high rates of adult plant mortality. High adult mortality and increased seed release correlated with increasing stand age, the occurrence of severe drought, and the likely presence of Phytophthora cinnamomi, a fungal pathogen which damages the root system, reducing water and nutrient uptake. There were no new recruits for the resprouter Hakea rostrata in this stand, but old plants continued to resprout from basal lignotubers and no mortality was observed. While recruitment of strongly serotinous shrub species is commonly described as being restricted to the immediate post-fire period, the present study illustrates that other events (e.g., senescence, drought, disease) can lead to recruitment of serotinous non-sprouters and may be important in the maintenance of populations during unusually long periods without fire. Top

Goldblum, D. and S.W. Beatty. (1999) Influence of an old field/forest edge on a northeastern United States deciduous forest understory community. Journal of the Torrey Botanical Society. 126: 335-443.

Abstract: We examined edge effects within a forest along old field boundaries in a mixed deciduous/hemlock forest community in upstate New York. Species composition and community structure of both forest understory and treefall gap vegetation were analyzed in two ways: first, we used belt transects to quantify changes in the understory community with distance from the forest edge, and second, we compared species composition of treefall gaps both near and distant from the edge. Exotic species and locally rare species were significantly more abundant at the forest edges than in the forest interior, while tree seedlings were less common at the forest edge. Species composition of treefall gaps near the old field/forest edge differed from composition of treefall gaps in the forest interior during most of the growing season. Treefall gaps at the forest edge, as a group, were compositionally more heterogeneous than treefall gaps distant from the edge. Top

Abstract: The size structure of the endemic New Caledonian conifer Agathis ovata is reported for sample stands in forest and maquis from three areas on ultramafic substrates in the south of the main island (Grand Terre). In closed forest Agathis ovata is typically represented by a low density of emergent adult trees with only limited evidence of seedling recruitment. In maquis, Agathis ovata is represented by individuals of all sizes, with seedlings and saplings abundant in most sample stands. Preliminary evidence from tree-ring studies indicates that rings may be annual. Estimated diameter growth rate is about 2 mm/yr for trees >10 cm dbh, and ring counts suggest tree ages of up to 400 years in maquis and 500 years in forest. Agathis ovata, and three other members of the Araucariaceae found in New Caledonia (Araucaria laubenfelsii, A. montana and A. rulei), are the only tree species which regularly occur scattered in maquis in this way, creating an unusual structural assemblage. No angiosperm tree species show this behaviour. The circumstances under which the Agathis ovata maquis stands arise and are maintained are the subject of further investigation. Preliminary evidence for tree ages indicates that these stands predate European arrival in New Caledonia and so are not the result of recent increases in the frequency and intensity of human disturbances. The presence of fire scars on many individuals, and location of most stands on slopes and spurs with outcropping laterite (cuirasse), suggests that this assemblage may owe its existence to the interplay of fire regime, topography and rockiness, and a resistance to fire in Agathis ovata which increases with plant size and age. Top

Abstract: This study addresses the secondary succession of abandoned Pinus resinosa (red pine) and Picea glauca (white spruce) plantations in upstate New York. Both red pine and white spruce are not regenerating in the unmanaged plantations. Successful regeneration of hardwood tree species in the white spruce plantations occurred only within the 25-30 years following planting. Higher light levels in the red pine stands have led to a greater degree of subsequent hardwood invasion than in the white spruce stands. The impact of abandoned conifer plantations will have long-term effects, altering the forest species composition for several hundred years. However, the plantations will eventually return to a natural forest composition, and expansion of planted conifers into adjacent undisturbed forests is unlikely.Top

Enright, N.J., Goldblum, D., Ata, P., and Ashton, D. H. (1997) The independent effects of heat, smoke, and ash on emergence of seedlings from the soil seed bank of a heathy Eucalyptus woodland in Grampians (Gariwerd) National Park, western Victoria. Australian Journal of Ecology 22: 81-88.

Abstract: The independent effects of smoke, ash, and wet and dry heat treatments on seedling emergence from the soil seed bank were tested for soils from fire-prone heathy woodlands in western Victoria. A total of 763 individuals from 56 species were recorded from the surface soil samples (which covered a total area of 1 m(2)). Both species richness and density of seedlings was greater for smoke- and heat-treated samples than for controls and ash-treated samples. However, only the density differences were significant. Mean seed bank densities for the smoke and heat treatments ranged from 855+/-70 m(-2) to 1080+/-58 m(-2) and are similar to estimates obtained elsewhere in Australia for heat-treated soils from dry sclerophyll communities. Of the 56 species recorded, 46 occurred in the smoke and heat treatments but only 33 in the control and ash treatments. The sudden increase in surface soil pH, exchangeable cations and extractable phosphorus which was associated with the ash treatment did not act as a trigger for germination in any of the species recorded here. Chemical constituents from smoke do appear to provide a stimulus separate from the effects of heat, but were not identified with any particular taxa. Top

Abstract: Treefalls are a common form of disturbance in northeastern United States forests. The resultant gaps contribute to a high degree of environmental heterogeneity in the understory of these forests. Plant density, plant cover, and species richness in understory plant communities were monitored for three years during the growing season, May - September. Differences between treefall gap and closed canopy vegetation were less pronounced early in the growing season for plant density and leaf cover. Species richness was significantly greater within treefall gaps during the entire growing season. Eight species were found in greater abundance within treefall gaps (i.e., gap-phase species), while one species was found more commonly under closed canopy. Ordination results suggest that time since gap creation and treefall gap size marginally affect the species composition of vegetation found within treefall gaps. Top

Project Summary: Forest response to climate change is well documented and significant. During past warming and cooling espisodes associated with glaciation, the forests of North America have tracked climate by shifting there ranges north and south across the continent. However, projections of human-induced climate change over the next several hundred years suggest that warming may be much faster than tree species have experienced in the past 18,000 years – in fact, probably over the past two million years. This rapid rate of climate change may severely impact many species' ability to reproduce and persist in regions where they are currently found. This problem may result in altered forest communities dominated largely of species with wide ecological tolerances. Sugar maple, an ecologically and economically important species in the deciduous forests of North America, is likely to be affected by altered climates near its northen limit. These effects may include altered growth rates, changes in survivorship and changes in the plant/soil community dynamics including long term associations with soil microbial partners. This project will evaluate the impact of anthropogenic climate change on soil microbial communities associated with sugar maple seedlings under an artificial temperature and precipitation manipulation experiment. It is designed to complement an ongoing project (NSF 0724256; Rigg and Goldblum) examining growth of sugar maple seedlings in response to human-induced temperature and precipitation change the boreal-deciduous forest boundary located in Lake Superior Provincial Park, Canada. Experimental plots, outfitted with rain-exclusion structures and infrared heat lamps, were established in May 2008. Since sugar maple is a dominant species in these forests it may drive much of the ecological change under modified climates. Soil microbial communities play a key role in geochemical processes including nutrient mineralization and soil organic matter transformation, but feedbacks between soil microorganisms and plant community composition/diversity are largely unknown. We will address two broad questions in habitats undergoing experimental climate change, 1) how will climate change alter soil microbial diversity and soil microbe community structure and 2) what role does the soil microbe community play in the feedback between climate change and soil respiration at the boreal-deciduous forest boundary where sugar maple is dominant. Microbial diversity will be evaluated in a three-fold manner: a) via polymerase chain reaction (PCR)-based product analysis, b) via cultivation of microbes, and c) via phospholipid fatty acid (PLFA) analysis.

There is no doubt that over long periods of time plant and microbial species respond to climate changes by range shifts, but using analogs from past climate change may not be entirely appropriate if forest ecologists wish to model biotic (both above- and belowground) response to climate change over the next century. Thus, field experiments that simulate the more pronounced and rapid temperature changes can provide constructive results identifying specific responses to alterations in temperature and atmospheric concentrations mimicking anthropogenic impacts. Thus, we aim to add to the growing knowledge base in forest ecology and microbiology that investigates the impact of climate change on natural ecosystems. Fully understanding and quantifying aspects of the carbon cycle in the plant-soil-atmosphere continuum will be critical in determining whether forest soils will become net sinks or sources of atmospheric carbon. A detailed understanding of the largely unstudied impact of climate change on soil microbes and how soil microbes affect carbon sequestration may prove to be a vital component in the expanding field of ecological impacts of global climate change. Further, we expect that our results will provide information on whether ecological thresholds exist beyond which sugar maples and their associated microorganisms may not survive, so that forest managers, soil scientists, modelers, and policy makers can begin to consider when environmental changes may become irreparably detrimental and monitor the environment for indications that those changes are imminent.Top

The focus of this project is to evaluate the impact of anthropogenic climate change on sugar maple seedlings and seeds at the species’ northern limit. Given the significant status of sugar maple in the forests of North America, we seek to assess the vulnerability of young sugar maple to alterations in air temperature and soil moisture. As a dominant species in these forests (and throughout eastern North America), sugar maple may drive much of the ecological change under modified climates. Both the ecological impact and nature of climate change are likely to be extremely complex and highly variable geographically. To address the vulnerability of terrestrial ecosystems to climate change, we will focus on an inherently sensitive ecosystem (an ecotone). We expect to identify which climate variables (temperature and/or precipitation) control growth and lead to plant stress or death, ultimately jeopardizing its continued presence in these forests and, by extension, across the northern portion of its range in eastern North America.

To date few environmental manipulation studies have considered the biotic impact due to changes in soil moisture (from both temperature and rainfall changes). By considering changes in rainfall regimes we anticipate providing a realistic picture of how young sugar maple plants are likely to cope with climate change. Given uncertainty of future climate changes, we expect that our experimental design of simulating a range of temperature and moisture regimes will capture conditions that sugar maple will experience in the northern part of its range sometime in the next 60-70 years. Specifically, we propose to address two objectives: 1) Determine the impact that future air temperature and precipitation regimes (based on Regional Climate Model [RCM] predictions) may have on in situ sugar maple seedlings at sugar maple’s current northern limit in central Ontario, Canada and 2) Determine the degree to which seeds from two source regions germinate and grow under field conditions in warmer and cooler climates within sugar maple’s current range.

These questions will be addressed in two ways. Firstly, using infrared heat lamps and rain exclusion structures, we propose to alter the temperature and precipitation regimes of in situ sugar maple seedlings at the current northern limit in central Ontario, Canada to mimic RCM-modeled conditions projected for the study area in the 2060s. Secondly, we will collect and reciprocally disperse sugar maple seeds from two sites representing extreme temperature conditions within sugar maple’s current range. We will utilize transition matrix modeling and associated analyses to examine the relative importance of survivorship and growth at the various life stages of sugar maple under several manipulated climate change scenarios. Further, by exposing sugar maple seeds from other portions of its range to a variety of climates, we expect to identify populations that may be more tolerant of the future climate so that forest managers may intervene, if necessary, to disseminate seed (or genetic material) to vulnerable populations.Top

Goldblum, D. and M. C. Kwit. 2010. The Relative Photosynthetic Contribution (Carbon Gain) of Old and New Fronds of the Wintergreen Fern Dryopteris carthusiana, Ontario, Canada. Presented at the Association of American Geographers annual meeting, April 16, 2010. Washington, D.C.

Rigg, L.S., D. Goldblum, and M. C. Kwit.2010. Modeling the Future of Sugar Maple at its Northern Limit: 2060 Here We Come. Presented at the Association of American Geographers annual meeting, April 16, 2010. Washington, D.C.

Kwit, M.C., D. Goldblum, and L.S Rigg. 2010. Sugar maple leaf phenology, light levels, carbon gain, and regeneration at and north of the current range limit. Presented at the Association of American Geographers annual meeting, April 14, 2010. Washington, D.C.

Goldblum, D. 2008. Sensitivity of corn and soybean yield in Illinois to past and future climate. Paper presented at the West Lakes Association of American Geographers regional meeting. November 15, 2008. Bloomington, IN.

Goldblum, D. 2007. Sensitivity of corn and soybean yield in Illinois to air temperature, precipitation, and climate change. Presented at the Association of American Geographers annual meeting. April 17, 2007, San Francisco, CA.

Rigg, L. (Presenter) and D. Goldblum, 2007. Projected population transitions for sugar Maple under different climate change scenarios. Presented at the Association of American Geographers annual meeting. April 17, 2007, San Francisco, CA

Goldblum, D. and N.J. Enright. 1999. Population ecology of Agathis ovata and Araucaria muelleri on serpentine substrates in New Caledonia. Poster presented at Third International Conference on Serpentine Ecology. Kruger National Park, South Africa. March 23, 1999.

Rigg, L, D. Goldblum, and N.J. Enright. 1995. Population and regeneration ecology of Araucaria laubenfelsii within closed forest and maquis, New Caledonia. Poster presented at Second International Conference on Serpentine Ecology in Noumea, New Caledonia. 31 July - 5 August 1995.

Goldblum, D. 1994. The effect of forest edges on exotic and uncommon herbaceous plant species. Paper presented at Association of American Geographers Annual Meeting. San Francisco, California. 4 April 1994.

The impact of fire regime on the regeneration success of cogeneric seeders and resprouters, Grampians, National Park, Australia. Invited to present at UW-Milwaukee, Department of Geography Colloquium series. Fall 1999.